Libro de Resúmenes - Unión Geofisica Mexicana AC

Geos, Vol. 30, No. 1, Noviembre, 2010
CLIMAS Y OCÉANOS DEL PASADO
with a cloud cover reduction over the North East Pacific (NEP), that leads to
increased SSTs, a weaker subtropical high and a lessening of the trade winds
as a positive feedback for further warming in response to increased atmospheric
greenhouse gases.
SE15-5
INTERMEDIATE AND DEEP-WATER MASS DISTRIBUTION
IN THE PACIFIC DURING THE LAST GLACIAL MAXIMUM
INFERRED FROM OXYGEN AND CARBON STABLE ISOTOPES
Herguera García Juan Carlos 1 , Herbert Tim 2 y Charles Chris 3
1 CICESE
2 Department of Geological Sciences, Brown University, RI, USA
3 Scripps Institution of Oceanography, California, USA
herguera@cicese.mx
Intermediate ocean circulation changes during the last Glacial Maximum (LGM)
in the North Pacific have been linked with Northern Hemisphere climate through
air-sea interactions, although the extent and the source of the variability of the
processes forcing these changes are still not well resolved. Modern ventilated
volumes and ages in the upper wind driven layer are related to the wind stress
curl and surface buoyancy fluxes at mid to high latitudes in the North Pacific. In
contrast, the deeper thermohaline layers are more effectively ventilated by direct
atmosphere-sea exchange during convective formation of Subantarctic Mode
Waters (SAMW) and Antarctic Intermediate Waters (AAIW) in the Southern
Ocean, the precursors of Pacific Intermediate Waters (PIW) in the North
Pacific. Recent results show a fundamental change in the carbon isotopic
gradient between intermediate and deep waters during the LGM in the eastern
North Pacific indicating a deepening of nutrient and carbon rich waters. These
observations suggest changes in the source and nature of intermediate waters
of Southern Ocean origin that feed PIW and enhanced ventilation processes in
the North Pacific, further affecting paleoproductivity and –export patters in this
basin. Furthermore, oxygen isotopic results indicate these changes may have
been accomplished in part by changes in circulation affecting the intermediate
depths during the LGM.
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